Blood Pressure (BP) The pressure the blood exerts against the inner walls of the blood vessels The pressure the blood exerts against the inner walls of the blood vessels Also is the force that keeps blood circulating continuously even between heartbeats Also is the force that keeps blood circulating continuously even between heartbeats Hypertension = high BP Hypertension = high BP Hypotension = low BP Hypotension = low BP

Measuring Blood Pressure Systolic pressure – the pressure in the arteries at the peak of ventricular contraction Systolic pressure – the pressure in the arteries at the peak of ventricular contraction Diastolic pressure – the pressure when the ventricles are relaxing Diastolic pressure – the pressure when the ventricles are relaxing Is measured as a fraction in millimeters of mercury (mm Hg) Is measured as a fraction in millimeters of mercury (mm Hg)

Measuring Blood Pressure Systolic number is always the higher # Systolic number is always the higher # “normal” adult BP is 120/80 “normal” adult BP is 120/80 Is frequently classified as idiopathic Is frequently classified as idiopathic Sometimes called the silent killer as there are no symptoms present for years Sometimes called the silent killer as there are no symptoms present for years Treatment methods usually are non-drug Treatment methods usually are non-drug Drug therapies are last attempt to control BP that is consistently high Drug therapies are last attempt to control BP that is consistently high

Measuring Arterial Blood Pressure Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Blood Pressure: Effects of Factors Temperature Temperature Heat has a vasodilation effectHeat has a vasodilation effect Cold has a vasoconstricting effectCold has a vasoconstricting effect Chemicals Chemicals Various substances can cause increases or decreasesVarious substances can cause increases or decreases Diet Diet

Factors Determining Blood Pressure Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Factors that may alter BP Age Age Weight Weight Time of day Time of day Exercise Exercise Body position Body position Emotional state Emotional state Various drugs Various drugs

Variations in Blood Pressure Human normal range is variable Human normal range is variable NormalNormal 140–110 mm Hg systolic 120/80 is “normal” 140–110 mm Hg systolic 120/80 is “normal” 80–75 mm Hg diastolic 80–75 mm Hg diastolic HypotensionHypotension Low systolic (below 110 mm HG) Low systolic (below 110 mm HG) Often associated with illness Often associated with illness HypertensionHypertension High systolic (above 140 mm HG) High systolic (above 140 mm HG) Can be dangerous if it is chronic Can be dangerous if it is chronic

Pressure Points When direct pressure is applied to these areas in the body, could decrease the loss of blood when a vessel becomes damaged. When direct pressure is applied to these areas in the body, could decrease the loss of blood when a vessel becomes damaged. Useful first aid measure to assist with hemostasis Useful first aid measure to assist with hemostasis

Palpable Pulses in the body

Peripheral Resistance The amount of friction encountered by the blood as it flows through the blood vessels The amount of friction encountered by the blood as it flows through the blood vessels Is affected mostly by a narrowing of the blood vessels (vasoconstriction) or blood volume (thickness) Is affected mostly by a narrowing of the blood vessels (vasoconstriction) or blood volume (thickness)

Sympathetic nervous system The major action on the vascular system is to cause vasoconstriction which in turn increases the BP The major action on the vascular system is to cause vasoconstriction which in turn increases the BP Example: standing up after lying down and the effect of gravity on circulation Example: standing up after lying down and the effect of gravity on circulation Exception: under stressful conditions, the SNS dilates the blood vessels supplying the skeletal muscles Exception: under stressful conditions, the SNS dilates the blood vessels supplying the skeletal muscles

Effects of the Kidneys on BP Alter blood volume as a regulating effect Alter blood volume as a regulating effect As BP increases beyond normal, allow more water to leave the body in the urine As BP increases beyond normal, allow more water to leave the body in the urine When arterial BP falls, the kidneys retain water, increasing blood volume and BP When arterial BP falls, the kidneys retain water, increasing blood volume and BP Renin (an enzyme) is released to form angiotensin II – a major vasoconstrictor Renin (an enzyme) is released to form angiotensin II – a major vasoconstrictor As sodium enters, water follows As sodium enters, water follows

Effects of Alcohol and Nicotine Nicotine increases BP by causing vasoconstriction Nicotine increases BP by causing vasoconstriction Alcohol and histamines cause vasodilation, thereby lowering BP Alcohol and histamines cause vasodilation, thereby lowering BP